The human visual system (HVS) is a remarkable optical device possessing tremendous resolving ability, dynamic range, and adaptivity. The HVS also performs an impressive amount of processing in early (preattentive) stages to identify salient features and objects. However, the HVS also has some properties that limit its performance under certain conditions. For example, veiling glare due to extremely high contrast can dangerously limit object detection in situations such as driving at night or driving into direct sunlight. On the other hand, conditions such as fog or haze can reduce contrast to a point that significantly limits visibility. The tristimulus nature of human color perception also limits our ability to resolve spectral distributions, so that quite different spectra may be perceived as the same color (metamers). Any form of color blindness exacerbates the problem.
Approaches have been proposed to enhance the power of the human visual system by applying on-the-fly optical image processing using see-through optical processing for image enhancement via a transparent display that modulates the color and intensity of a real-world observation. In contrast to ‘see-through’ augmented reality (AR) displays, such approaches spatially filter incoming light at an observer's position, so that image processing operations such as contrast reduction, contrast enhancement, or color manipulation may be achieved with reduced latency compared to video-based AR systems. For example, such approaches may use a spatial light modulator (such as a transparent LCD panel) in the optical path to perform a variety of useful image processing operations directly on the light entering the human eye to locally filter a real-world scene to enhance the visual performance of a human observer.
However, the inventors herein have recognized that such approaches may be limited by the optics of near-eye displays. For example, processing pixels on a see-through display device near an eye of a user may cause a shape formed by the processed pixels to be out of focus so that the ability of the system to perform high-resolution image processing is degraded. Further, previous approaches may rely on optical elements to focus the incoming light field to achieve these high-resolution effects. Such bulky designs may be impractical for near-eye see-through displays, e.g., glasses or other head-mounted see-through display devices. Further, even in cases where a see-through display device is not physically close to an eye of a user, but remains close enough that a point being viewed projects to different rays for the eyes of one or more viewers, such approaches may only attenuate light incident to the display device based on a position of the incident light on the display and may not attenuate light based on the direction of the incident light.